Dr. Duchene is a fellow associate, Department of Urology, University of Iowa, Iowa City, IA.
Choose the single best answer for each question.

1. A 55-year-old man presents to his primary care physician with complaints of abdominal pain, malaise, and weight loss over the past several weeks. The discomfort is not affected by change of position and is constant in nature. Physical examination is remarkable only for a slightly elevated blood pressure and mild edema in the extremities. Laboratory testing reveals a serum creatinine level of 1.2 mg/dL, which is slightly elevated from the patients baseline. An ultrasound scan reveals mild bilateral hydronephrosis. Which of the following tests would be the most helpful to further evaluate this patient?

Questions 3 and 4 refer to the following case study:
A 42-year-old woman with recurrent nephrolithiasis presents to the emergency department with flank pain and anuria. A CT scan using stone protocol demonstrates no evidence of nephrolithiasis but shows moderate bilateral hydronephrosis due to paraaortic lymphadenopathy and tissue thickening around the ureters. Laboratory testing reveals a serum creatinine level of 8.1 mg/dL and a potassium level of 6.2 mEq/L.